Zinc electroplating electrolyte and process

ABSTRACT

In accordance with certain of its aspects this invention relates to a process of producing bright zinc electrodeposits which comprises passing current from an anode to a metal cathode through an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, a bathsoluble polyether, and at least one non-aromatic Alpha , Beta unsaturated carbonyl compound for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode.

United States Patent Harbulak [451 June 13, 1972 [54] ZINC ELECTROPLATING ELECTROLYTE AND PROCESS 21 Appl. No.: 60,734

[52] US. Cl ..204/55 R, 204/DIG. 2

[51] Int. Cl. ..C23b 5/10, C23b 5/46 [58] Field of Search ..204/55 R, 55 Y, 43.44; 106/1; 1 17/ l 30 E [56] References Cited UNITED STATES PATENTS 3,005,759 10/1961 Safranek et a1. ..204/55 R 3,296,104 1/1967 Eppensteiner ..204/55 R 3,574,067 4/1971 Spiro ..204/55 R FOREIGN PATENTS OR APPLICATIONS 1,149,106 4/1969 Great Britain ..204/55 R Primary ExaminerG. L. Kaplan AttorneyLewis C. Brown, Kenneth G. Wheeless and Robert P. Grindle 57 ABSTRACT In accordance with certain of its aspects this invention relates to a process of producing bright zinc electrodeposits which comprises passing current from an anode to a metal cathode through an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, a bath-soluble polyether, and at least one non-aromatic a, ,8- unsaturated carbonyl compound for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode.

14 Claims, No Drawings ZINC ELECTROPLATING ELECTROLYTE AND PROCESS This invention relates to the electrodeposition of bright zinc from cyanide-free baths. More particularly this invention relates to improved zinc plating bath compositions, to methods of using and preparing such bath compositions and to improved surfaces having bright zinc electrodeposits thereon.

Alkaline solutions containing complex compounds of zinc and alkaline metal pyrophosphates have been proposed as a potential replacement for cyanide baths and cyanide processes for the electrodeposition of bright zinc. Such substitutions have been proposed because of the troublesome and costly disposal problems which have become associated with the use of cyanide electroplating baths. The electrodeposition of zinc using a pyrophosphate bath, however, may give relatively poor low current density coverage, spore formation, roughness, insufficient brightness, and relatively non-uniform deposits. In addition, anode corrosion may result in passivation of the anode and undesirable precipitates may form during operation thus tending to clog filter systems and sometimes result in intermittent operation necessitated by frequent changes of filter media.

The use of phosphates may also produce waste disposal problems since phosphates are not easily removed and may promote the growth of undesirable aquatic plant life if discharged into streams. These disposal disadvantages further limit the acceptance of pyrophosphate zinc plating bath compositions in industrial applications.

Non-cyanide zincate zinc plating baths have also been proposed as substitutes for cyanide containing systems. However, the bright plating current density range of these baths is quite limited, making the plating of articles of complex shape difficult, if not impossible. Since the addition of cyanide to these non-cyanide zincate baths greatly improves the bright range of the deposits, platers tend to revert back to the lowcyanide zincate systems, thus negating the non-cyanide feature of the original bath.

Highly acidic zinc plating baths have been known for some time and such baths must be cyanide-free. These systems have extremely poor low current density coverage and fmd their chief application in the strip line plating of wire and sheet steel using very high but narrow current density ranges. Thus, they are not suited for plating objects of any complexity in shape or for normal decorative, rust-proofing application.

More recently, mildly alkaline or acidic cyanide-free zinc plating baths containing large amounts of buffering and complexing agents to stabilize both pH and solubilize the zinc ions at the pH values involved have been employed to overcome the objections of using cyanide-containing zinc plating processes. In general these zinc baths consist of an aqueous solution containing at least one simple zinc salt, (for example zinc sulfate, zinc chloride, zinc acetate), and an ammonium salt (for example an ammonium halide, or ammonium sulfate). The zinc bath may additionally contain an organic zinc complexing agent such as a hydroxy carboxylic acid or salts thereof, ethylenediamine tetra acetic acid or salts thereof, and/or similar materials to prevent the precipitation of zinc from the bath as the insoluble hydroxide at higher values of pH, i.e. pH 5.5 and above. These baths are typically operated in the pH range of about 4 to 8.

Additions of bath soluble polyoxyalkylene compounds to zinc baths of the foregoing type may result in improved throwing power, hardness, and luster of the zinc deposits. A particularly useful and representative bath composition may consist of:

ZnCl 50 g/l ln order to improve and increase the brightness, luster and throwing power of zinc deposits from these baths, certain aromatic organic additives are used as brighteners. While these brighteners provide generally satisfactory zinc deposits from freshly prepared zinc baths, the deposits tend to be dull in low current density regions. In addition, because of the nature of the aromatic organic additives used as brighteners, highly objectionable oily decomposition products may form on prolonged bath electrolysis. These oily materials are not soluble in the bath and float on the surface where they adhere to parts as they are placed in and removed from the bath causing pitting problems during the plating cycle, blotching and nonuniform results in subsequent chromate post-treatment of the zinc deposits. Removal of these oily decomposition products is difficult and troublesome, and as a result zinc electroplating processes of this type have found only limited acceptance in the plating industry.

It is an object of this invention to provide novel processes and compositions for electroplating of bright zinc plate especially from mildly acidic, neutral, or mildly alkaline zinc plating baths. Other objects of the invention will be apparent to those skilled in the art upon inspection of the following detailed description.

In accordance with certain of its aspects, this invention relates to a process of producing bright zinc electrodeposits which comprises passing current from an anode to a metal cathode through an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, a bath-soluble polyether, and at least one non-aromatic a,[3-unsaturated carbonyl compound for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode.

Typical a,,B-unsaturated carbonyl compounds which may be employed in the present invention include non-aromatic organic compounds characterized by the following general structure:

wherein R R R and R may be hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy of one-four carbon atoms, hydroxy, halogen (Cl, Br, F, I), amino (-NH or a part of a non-aromatic carboxcyclic chain. R may contain inert substitucnts (i.e. bath compatible groups such as oxygen, halogen, alkyl, hydroxy, etc.) and R are each preferably of one-l0 carbon atoms with the total carbon atoms of R R R and R no more than 25 carbon atoms. Additionally, R, and R may form part of the same closed non-aromatic ring, as can R and R R and R or R, and R for example:

wherein n is an integer of from 2 to 6 representing the number of carbon atoms in group C,,, and C, is a divalent alkylene CH -Cl-l Cl-l -CH CI-I,CH etc.) or a divalent alkenylene group (such as of two-six carbon atoms. When one ore more of R is an alkyl group, at least one R is preferably a lower alkyl group of one-six carbon atoms such as methyl, ethyl, n-propyl, ipropyl, n-butyl, i-butyl, sec.-butyl, tert.-butyl, pentyl, or hexyl. When one or more of R is an alkenyl group at least one R is preferably a lower alkenyl group of two-six carbon atoms such as allyl, methallyl, pentenyl or hexenyl. When two of the R groups combine to fonn a cycloalkyl group the cycloalkyl group may have four-eight carbon atoms such as cycloburyl,methylcyclobutyl, dimethylcyclobutyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, cyclohexyl, methylcyclohexyl, etc. When two or more of the R groups combine to form a cycloalkenyl group ,the cycloalkenyl group may have four-eight carbon atoms such as eyclobutenyl, methylcyclobutenyl, ethylcyclobutenyl, cyclopentenyl, methylcyclopentenyl, cyclopentadienyl, i-propylcyclopentenyl, cyclohexenyl, dirnethylcyclohexenyl, ethylcyclohexenyl, etc.

The enol forms of the B-dicarbonyl compounds (or 1,3- dicarbonyl compounds) may also be used. The enol form of any 1,3-diketone may be employed. Compounds such as afiunsaturated cyclopentanoes, cyclohexanones, as well as substituted and unsubstituted tropones and mixtures thereof may be used.

When the non-aromatic a,B-unsaturated carbonyl compound is an mil-unsaturated aldehyde it may have the following structural formula:

csta/ R/ \H wherein each R is independently hydrogen or an organic radical of from one-l0 carbon atoms. The R groups on the a or 3 carbon atoms may be joined to form cyclic a,B-unsaturated aldehydes. When R is an organic radical, R may be an alkyl, alicyclic, or an alkenyl group of from one-l0 carbon atoms; organic radicals of from one to 6 carbon atoms are preferred. When R is an alkyl radical, lower alkyl radicals (of one to six carbon atoms) are suitable. Specific lower alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, pentyl, and hexyl. Other examples of suitable R groups include cyclopentyl, cyclohexyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, allyl, and vinyl groups.

The following compounds are examples of typical a,fi-unsaturated carbonyl compounds which may be employed according to the invention and illustrate the generalized structural formulas given above:

Acrolein O HzC C H-iL-H Aerylamide- O H2C=CH-( I NHQ Acrylic acid O HzC=CHii-OH Methacrolein O H zC=C-ii-H Crotonaldehyde Mesityl oxide.

Phorone Sorbic aldehyde Sorbic acid Cltral 2,4,6-octatriena1 fi methyl heme-2- enedial.

4-(3-cyolohexene)-3- butene-Z-one.

1,6-dl-(3-cyclohexene)- IA-pentadlene-B-one.

Isojasmone Plperitone Ionone 6-methy1-5,rdihydrobenzaldehyde.

Oarvone C=CH2 Exceptionally good results are obtained according to the invention using at least one a,B-unsaturated carbonyl compound selected from the group consisting of isojasmone, 6- methyl-S,6-dihydrobenzaldehyde, citral, and mesityl oxide having the formulas:

wherein it is understood that all unsatisfied valences of carbon atoms are attached to hydrogen atoms, and wherein each vertex of the formulas represents a carbon atom.

The amount of a,B-unsaturated carbonyl compound employed in the compositions of the invention is an amount sufficient to provide improved bright zinc electroplate when compared with a bath composition which is identical in all respects save that said bath composition contains no a,B-unsaturated carbonyl compounds of the invention herein. The improved bright zinc electroplate deposits of the invention herein are generally characterized as showing improvement in at least one of the properties such as freedom from dullness in lower current density areas, improved ductility, and uniformity of lustrous deposit throughout the plating current density range. In general, amounts of a,B-unsaturated carbonyl compounds of about 0.01 g/l 4.0 g/l (preferably about 0.05 0.25 g/l) may be used. The use of larger amounts ordinarily does not provide a corresponding increase in brightness and may cause partial or severe striations in low current density areas.

The polyether which may be employed in amounts of about 1.0-25 g/l (preferably about 2-10 g/l) in combination with the a,B-unsaturated carbonyl compounds in amounts of about 0.01 g/l 4.0 g/l (preferably about 0.05 0.25 g/l) may include aromatic ethers or aliphatic polyethers. Preferably the polyether is a polyalkoxylated alkyl phenol. Typical polyalkoxylated alkyl phenols include polyethoxylated alkyl phenols having the formula:

wherein R represents an alkyl group of from eight to 16 carbon atoms (preferably nine carbon atoms) and k is an integer of from two to 50 (preferably from about to 30).

Other polyethers which may be employed in amounts of about 1.0 25 g/l (preferably about 2-10 g/l) in combination with a,B-unsaturated carbonyl compounds in amounts of about 0.01 4.0 g/l (preferably about 0.05 0.25 g/l) may include aliphatic polyethers characterized by the following general formula:

wherein R represents hydrogen or methyl and p is an integer of from about 7 to 50 (preferably from about 20 to 40).

The a,,B-unsaturated carbonyl compounds and the polyether compounds used in combination in the novel bright zinc electroplating baths of the invention may contain inert substituents. By an inert substituent as the term is used herein is meant any bath compatible group which does not destroy, reduce, interfere with, or hinder the formation of the bright zinc electrodeposits described herein. Typical examples of inert substituents include the halogens (chloride, bromide, iodide, and fluoride); amines (including amino and heterocyclic nitrogen groups such as piperidinyl), hydroxy groups, alkoxy groups (such as methoxy, ethoxy, propoxy, etc.), alkyl groups, sulfate, etc.

According to a particular aspect of the invention, a mixture of the non-aromatic B-unsaturated carbonyl compound and the polyether (preferably an alkyl-aryl polyether) may be employed in combination with other additives. Examples of such cooperating mixtures include a 50:1 (parts by weight) combination of the reaction products of nonyl phenol with about 15 moles of ethylene oxide and an a,B-unsaturated carbonyl compound. Other suitable weight ratios of ethoxylated alkyl phenol polyether and preferably non-aromatic a,B-unsaturated carbonyl compounds include weight ratios of about :1 to l/2:1, respectively. Mixtures of 0:,B-unsaturated carbonyl compounds may also be used and wherever mixtures of a,/3-unsaturated carbonyl compounds are employed, the weight ratios referred to herein refer to the total weight of all of the afi-unsaturated carbonyl compounds combined.

The basis metal onto which the bright zinc deposits of this invention may be applied may include ferrous metals such as steel; cast iron; copper including its alloys such as brass, bronze, etc.; die cast metals which may bear a plate of another metal such as copper; thin coatings, e.g. of silver, nickel, or copper, on a non-conductive article (such as a rigid or flexible plastic) which coating may be applied by chemical reductive techniques, such as electroless plating, etc.

According to another aspect of the invention the preferred operating conditions, such as pH, temperature, and current density may vary depending upon the particular bath composition and the nature of the article receiving the layer of bright zinc electrodeposit. In general, good, bright zinc electrodeposits may be obtained within a specific range of operating conditions. For example, when the pH is within the desired range (i.e. about 1.0 10.0, preferably about 4.0 8.0) a zinc electrodeposit may attain maximum brightness and the current efficiency may also be optimized.

The bright zinc electroplating processes using the compositions of the invention may be carried out at temperatures of about 10 60 C. (preferably 15 35 C.) either with or without agitation. Using average current densities of 0.5 5.0 amperes per square decimeter (ASD), bright zinc electrodeposits having average thicknesses of 0.25 25 microns may be obtained using plating times which may average 0.5 minutes.

If necessary, vigorous and uniform agitation of the plating bath composition may be provided either by mechanical movement of the article being plated or by solution agitation during the electrodeposition. Such agitation may permit the use of high plating current densities on the article being plated. During the plating operation, it is desirable to keep metallic contaminants at very low concentration levels in order to insure a bright zinc electrodeposit. Such contamination from metal ions, (such as cadmium, copper, iron, and lead) may be reduced or eliminated through conventional purification methods. Other types of contaminants (such as organic contaminants) may also be eliminated or reduced by circulation of the zinc electroplating solution through a suitable filter media such as activated carbon or types of ion exchange or absorption media.

Some of the a,B-unsaturated carbonyl compounds of this invention may have only limited solubility in aqueous solutions. In order to introduce the required amount of these materials into the plating bath, it is most advantageous to first dissolve the appropriate a,/3-unsaturated carbonyl compounds, such as isojasmone, piperitone, citral, 6-methyl-5,6-dihydrobenzaldehyde, etc. in a suitable bath soluble solvent. Suitable bath soluble solvents in which the a,,6-unsaturated carbonyl compounds are readily soluble are methanol, ethanol, isopropanol, ethylene glycol-monoethyl ether (i.e., cellosolve), acetone, etc. A concentration of about 25 to 50 g/l of the a,,B-unsaturated carbonyl compounds in a suitable solvent provides a satisfactory stock solution for addition to the plating bath. In this manner the carbonyl compounds of this invention can be easily added to the plating solution while obtaining rapid dispersion and optimum miscibility.

The following examples are submitted for the purpose of illustration only, so that those skilled in the art of zinc plating may better understand the operation of the invention. These examples are not to be construed as limiting the scope of the invention in any way.

EXAMPLE I An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts The ammonium chloride, citric acid, and ammonium hydroxide were employed as buffers, complexing agents and pH adjusting agents. To this basic zinc-containing composition there were added the following in the indicated amounts:

INGREDIENT AMOUNT Citral 0.15 g/l Nonylphenol reacted with moles ethylene oxide 4 g/l The bath wm adjusted to a pH (electrometric) of 7 at a temperature of 24 C.

A 1,280 gram load of /4 steel hexagonal nuts, suitably cleaned and pickled, was barrel plated in the above bath for 60 minutes, using a small horizontal plating barrel revolving at 5 rpm. The bath temperature was about 24 C., the cell current was 7.5 amperes, and the cell voltage was 2.2 volts. The zinc deposit obtained on the nuts was very bright and uniform, while the deposit color, adhesion, ductility and coverage were all excellent. The thickness of the deposit, measured with a Magnagage on the flat edges and faces of several randomly selected nuts, was found to be a very uniform 1.15 microns (0.00045 inches).

EXAMPLE II An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared:

The pH of this bath was 5.5 (electrometric) at 25 C. as prepared and was used without further modification.

An elliptically shaped copper plated zinc die cast faucet handle measuring about 5 X 3 X 0.8 cm was rack plated in the above zinc plating bath for 20 minutes at 0.5 amps cell current, while the bath was agitated by means of a stirrer. The resulting zinc deposit was very uniform in appearance and covered the very low current density areas very well, while also plating sound, smooth, glossy deposits at the high current density edges without any evidence of dullness, graininess, or treeing. After rinsing, the deposit was treated in a a vol/percent nitric acid solution and the color and brightness of the zinc deposit then rather resembled buffed sterling silver.

EXAMPLE In An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and evaluated in a 250 ml Hull Cell at about 24 C. using 1 amp cell current, 5 minutes plating time, and employing a smali magnetic stirrer to mildly agitate the bath.

INGREDIENT AMOUNT ZnSO;H,O g/l NH,Cl 100 g/l Citric Acid H O I00 g/l Nl-LOH sufficient to g ive pH 4 (electrometric) Blend of equal parts of the compound HO-(Cl-l,-CI-l,-

0),,H wherein n is about 7 and 36 respectively 6-methyl-5,6-dihydrobenzaldehyde EXAMPLE IV An aqueous bright zinc electroplating bath was prepared with the same composition as described in Example I. The following ingredients were then added in the indicated amounts:

INGREDIENT AMOUNT Reaction product of 1 mole nonylphenol reacted with 15 moles of ethylene oxide 4 g/l Carvone 0.2 mil] Citral 0.02 [Ill/I A Hull Cell test was then carried out using the same conditions of current, time, temperature, etc. as listed in Example III. The resulting zinc deposit obtained on the Hull Cell panel was brilliant and lustrous across the entire current density range of the test panel. In addition, the zinc deposit completely covered the back of the panel indicating very good low current density coverage. There was a faint haziness at the high current density end of the panel before treating the deposit in a chromate conversion solution. After the conversion coating dip the deposit was bright throughout the entire current density range.

EXAMPLE V Furfuraldehyde is a heterocyclic carbonyl compound known in the art as a brightener in zinc plating baths. In order to comparatively evaluate the a,B-unsaturated carbonyl compounds of this invention against a known zinc brightener, the

conditions of Example IV were repeated with the only exception being that the a,/8-unsaturated carbonyl compounds (carvone and citral) of the invention were replaced with 0.1 ml/l of furfuraldehyde. The resulting zinc deposit on the Hull Cell panel was dull, dark grey, and non-reflective over the entire high current density third of the panel. The remaining two thirds of the panel were covered with a very hazy semi-bright to bright zinc deposit, except that about 1 cm. from the low current density edge of the panel there was a dull, dark band about 1 cm. wide.

Increasing the furfuraldehyde concentration to 0.3 ml/l and repeating the test improved the deposit over the low current density two-thirds of the panel to the point where the deposit was only lightly covered with haze. However, the high current density portion of the panel remained dull, grey and nonreflective.

EXAMPLE VI An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and evaluated in a 250 ml. Hull Cell at about 22 C. using 1 amp cell current, 5 minutes plating time, and employing a small magnetic stirrer to mildly agitate the bath.

INGREDIENT AMOUNT ZnCl 50 g/l NI-I,Cl 125 g/l Citric Acid Monohydrate 60 g/l NI-LOI-I sufficient to give a pH of 7 (electrometric) Reaction product of 1 mole of nonylphenol and moles of ethylene oxide 4 g/l Piperitone 0.2 ml/l The zinc deposit obtained on the Hull Cell test panel was uniformly bright across the entire panel. The deposit had a light haze or cloudy blush which disappeared after a conversion coating post-treatment. The entire back of the test panel was completely zinc plated indicating excellent throwing power.

EXAMPLE VII An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and evaluated in a 250 ml I-Iull Cell at about 22 C. using 1 amp cell current, 5 minutes plating time, and em- The zinc deposit obtained on the Hull Cell test panel was completely ductile and very uniformly bright and lustrous across the entire panel. In addition, the deposit completely covered the back of the test panel indicating excellent throwing power and low current density coverage.

EXAMPLE VIII An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and tested in a 250 ml I-Iull Cell at about 22 C. using 1 amp cell current, 5 minutes plating time, and employ ing a small magnetic stirrer to mildly agitate the bath.

INGREDIENT AMOUNT ZnCl, 50 g/l NI-LCI g/l Citric Acid Monohydrate 60 g/l NH OH sufficient to give a pH of 7.

Reaction product of 1 mole of nonylphenol and I5 0 (electrometric) moles of ethylene oxide 4 g/l 4-( 3-cyclohexene )-3-butene- 2-one 0.2 g/l The zinc deposit obtained on the Hull Cell test panel was uniformly bright except for a 1 cm wide band at the high current density edge of the panel which was somewhat hazy and a similar 1 cm wide band at the low current density edge of the panel which ranged from hazy to dull.

EXAMPLE IX An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and tested in a 250 ml I-Iull Cell at about 23 C. using 1 amp cell current, 5 minutes plating time, and employing a small magnetic stirrer to mildly agitate the bath.

The zinc deposit obtained on the Hull Cell test panel was uniformly bright across the entire panel except that the high current density half of the panel was somewhat hazy and rather resembled a semi-bright nickel deposit.

EXAMPLE X An aqueous bright zinc electroplating bath composition containing the following ingredients in the amounts indicated was prepared and evaluated in a 250 ml I-Iull Cell using 1 ampere cell current, 5 minutes plating time, and employing a small magnetic stirrer to mildly agitate the solution.

INGREDIENT AMOUNT 21161 13.4 g/l NI-LCI 280 g/l Nonylphenol reacted with 15 moles ethylene oxide 4 g/l Citral 0.2 g/l 6-methyl-5,6-

dihydrobenzaldehyde 0.1 g/l pH 6 electrometric as prepared Temperature 25 C.

The zinc deposit obtained from the above bath formulation was uniformly bright across the entire current density range of the Hull Cell panel.

Using a 50 vol/percent aqueous sulfuric acid solution the pH of the zinc bath was then lowered to 1.4 electrometric and a second test panel was plated. Again the zinc deposit thus obtained was uniformly bright across the entire panel.

EXAMPLE Xl An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and evaluated in a 250 ml Hull Cell using 1 ampere cell current, 5 minutes plating time, about 25 C. bath temperature and employing a small magnetic stirrer to provide mild solution agitation.

INGREDIENT AMOUNT ZnCl g/l NH Cl 233 g/l NH,OH (29% NH;,) sufficient to give a pH of 9.7 eiectrornetric Nonylphenol reacted with moles ethylene oxide 4 g/l carvone 0.1 g/l The zinc deposit thus obtained on the Hull Cell test panel was uniformly bright across the entire current density range of the panel. The deposit had a light bluish, uniform, haze which was readily removed by treating the deposit in a 0.5 vol/percent nitric acid solution.

EXAMPLE XII An aqueous bright zinc electroplating bath composition containing the following ingredients in the indicated amounts was prepared and evaluated in a 250 ml. Hull Cell at 40 C.

using 1 amp. cell current, 5 minutes plating time and employing a small magnetic stirrer to mildly agitate the bath:

Zinc acetate 16 g/l Glacial acetic acid to give pH 4.0 electrom etric Nonylphenol reacted with 15 moles ethylene oxide 5 g/l Citral 0.2 g/l 5-methyl-5,6-

dihydrobenzaldehyde 0.1 g/l The zinc deposit obtained on the Hull Cell test panel was bright across the entire panel but covered with a uniform haze or cloud. On dipping the deposit in 0.5 vol/percent HNO the haze was eliminated.

The panel was uniformly bright from the low current density region (0.1 asd) to the high current density region 6.0 asd).

Although this invention has been illustrated by reference to specific embodiments, modifications thereof which are clearly within the scope of the invention will be apparent to those skilled in the art.

I claim:

1. A method of producing bright zinc electrodeposits which comprises passing current from an anode to a metal cathode through an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, 1.0 to 25 grams per liter of at least one bath-soluble polyether selected from the group consisting of aromatic ethers and aliphatic ethers of the formulas:

-O (CHzC HQOMH wherein R is an alkyl group of eight-16 carbon atoms and k is an integer 2-50, and

wherein R is hydrogen or a methyl group and p is an integer of about 7-50, and 0.01 to 4.0 grams per liter of at least one nonaromatic cap-unsaturated carbonyl compound for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode.

2. The method as claimed in claim 1 wherein the non-aromatic imp-unsaturated carbonyl compound has the formula:

wherein each of R is independently selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy of onefour carbon atoms, hydroxy, halogen, or amino.

3. The method as claimed in claim 1 wherein the non-aromatic a,B-unsaturated carbonyl compound has a formula selected from the group consisting of:

wherein n is an integer 2-6 representing the number of carbon atoms in the group C and C, is a divalent alkylene or alkenylene group of two-six carbon atoms.

4. The method as claimed in claim 1 wherein the a,B unsaturated carbonyl compound has the formula:

wherein each R is independently hydrogen or an organic radical of one-l0 carbon atoms.

5. The method as claimed in claim 1 wherein at least one a,B-unsaturated carbonyl compound is selected from the group consisting of citral, 6-methyl-5,o-dihydrobenzaldehyde, carvone, piperitone, isojasmone, 4-( 3-cyclohexene)-3-butene- 2-one, and mesityl oxide.

6. The method as claimed in claim 1 wherein the bath-soluble polyether is of the formula:

wherein R is an alkyl group of eight-l 6 carbon atoms and k is an integer 2-50.

7. The method as claimed in claim 1 wherein the bath-soluble polyether is of the formula:

wherein R is hydrogen or a methyl group and p is an integer of about 7-60.

8. A composition for providing bright zinc electrodeposits which comprises an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, 1.0 to 25 grams per liter of at least one bath-soluble polyether selected from the group consisting of aromatic ethers and aliphatic ethers of the formulas:

wherein R is an alkyl group of eight-l6 carbon atoms and k is an integer 2-50, and

wherein R is hydrogen or a methyl group and p is an integer of about 7-50, and 0.01 to 4.0 grams per liter of at least one nonaromatic a,B-unsaturated carbonyl compound.

9. A composition as claimed in claim 8 wherein the non-aromatic a,[3-unsaturated carbonyl compound has the formula:

wherein each of R is independently selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy of one-four carbon atoms, hydroxy, halogen, or amino.

10. A composition as claimed in claim 8 wherein the nonaromatic a,B-unsaturated carbonyl compound has a formula selected from the group consisting of:

wherein n is an integer 2-6 representing the number of carbon atoms in the group C and C, is a divalent alkylene or alkenylene group of two-six carbon atoms.

11. A composition as claimed in claim 8 wherein the (1,3- unsaturated carbonyl compound has the formula:

wherein R is an alkyl group of eight-l 6 carbon atoms and k is an integer 2-50.

14. A composition as claimed in claim 8 wherein the bathsoluble polyether is of the formula:

wherein R is hydrogen or a methyl group and p is an integer of about 7-60. 

2. The method as claimed in claim 1 wherein the non-aromatic Alpha , Beta -unsaturated carbonyl compound has the formula: wherein each of R1 4 is independently selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy of one-four carbon atoms, hydroxy, halogen, or amino.
 3. The method as claimed in claim 1 wherein the non-aromatic Alpha , Beta -unsaturated carbonyl compound has a formula selected from the group consisting of:
 4. The method as claimed in claim 1 wherein the Alpha , Beta -unsaturated carbonyl compound has the formula: wherein each R'' is independently hydrogen or an organic radical of one-10 carbon atoms.
 5. The method as claimed in claim 1 wherein at least one Alpha , Beta -unsaturated carbonyl compound is selected from the group consisting of citral, 6-methyl-5,6-dihydrobenzaldehyde, carvOne, piperitone, isojasmone, 4-(3-cyclohexene)-3-butene-2-one, and mesityl oxide.
 6. The method as claimed in claim 1 wherein the bath-soluble polyether is of the formula: wherein R is an alkyl group of eight-16 carbon atoms and k is an integer 2-50.
 7. The method as claimed in claim 1 wherein the bath-soluble polyether is of the formula: wherein R'' is hydrogen or a methyl group and p is an integer of about 7-60.
 8. A composition for providing bright zinc electrodeposits which comprises an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, 1.0 to 25 grams per liter of at least one bath-soluble polyether selected from the group consisting of aromatic ethers and aliphatic ethers of the formulas: wherein R is an alkyl group of eight-16 carbon atoms and k is an integer 2-50, and wherein R'' is hydrogen or a methyl group and p is an integer of about 7-50, and 0.01 to 4.0 grams per liter of at least one non-aromatic Alpha , Beta -unsaturated carbonyl compound.
 9. A composition as claimed in claim 8 wherein the non-aromatic Alpha , Beta -unsaturated carbonyl compound has the formula: wherein each of R1 4 is independently selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy of one-four carbon atoms, hydroxy, halogen, or amino.
 10. A composition as claimed in claim 8 wherein the non-aromatic Alpha , Beta -unsaturated carbonyl compound has a formula selected from the group consisting of:
 11. A composition as claimed in claim 8 wherein the Alpha , Beta -unsaturated carbonyl compound has the formula: wherein each R'' is independently hydrogen or an organic radical of one-10 carbon atoms.
 12. A composition as claimed in claim 8 wherein at least one Alpha , Beta -unsaturated carbonyl compound is selected from the group consisting of citral, 6-methyl-5,6-dihydrobenzaldehyde, carvone, piperitone, isojasmone, 4-(3-cyclohexene)-3-butene-2-one, and mesityl oxide.
 13. A composition as claimed in claim 8 wherein the bath-soluble polyether is of the formula: wherein R is an alkyl group of eight-16 carbon atoms and k is an integer 2-50.
 14. A composition as claimed in claim 8 wherein the bath-soluble polyether is of the formula: wherein R'' is hydrogen or a methyl group and p is an integer of about 7-60. 